The Pb-Pb system of chronometry [1]} yields absolute ages under reasonable assumptions, but with somewhat less precision and, perhaps, more susceptibility to systematic error due to the possibility of environmental contamination [2]}. While there is good agreement with the short-lived isotope results on the main points that CAI's are the oldest objects and have a much narrower age spread than chondrules, there is controversy over whether chondrule formation began at t = 0. At present, there are only 22 chondrules with Pb-Pb ages reported and they yield a mean age of 1.4 \(\pm \)  1.3 Myr, consistent with results from the short-lived isotopes [3]}, [1]}, [5]}. The fact that some chondrules yield dates consistent with t = 0, leads to the claim that chondrule formation began at that time, but given the small number of objects and the large error bars involved this is not yet convincing to all. In addition, reconciliation with the \(^{26}\) Al data requires that the isotope was not distributed evenly in the early solar system [1]}, [5]}, which has its own set of issues [8]}, [2]}. While the matter is unresolved, a gap in time between CAI and chondrule formation of \(\sim \) 1 Myr is not ruled out by currently available Pb-Pb ages, in our opinion.
